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Full text of "Treatise On Applied Analytical Chemistry(Vol-1)"




This is the liquid part of distilled wool fat, consisting of free fatty acids
(40-60%), hydrocarbons and a little cholesterol and isocholesterol.

It is a more or less turbid liquid of a reddish-brown colour and more
or less fluorescent and with a peculiar odour recalling that of wool fat. It
is soluble in 95% alcohol, ether, benzine, etc.

With cone, sulphuric acid, its chloroform solution gives a red coloration
with a green fluorescence (cholesterol). It may be adulterated with mineral
or resin oils or resin.

Its analysis includes the following:

1.  Acid and Saponification Numbers and Unsaponifiable Matter.
—Use is made, of the methods described in the preceding chapter (General
Methods, 7 and 19).

2.  Mineral and Resin Oils.—From 50 grams or more of the oleine
the unsaponifiable substances are extracted by the ordinary methods, and
their specific gravity, index of refraction, rotatory power (in about 3-4%
benzene solution and in a tube 10 cm. long at a temperature of 18-20°)
and iodine number determined.

The presence of mineral oil may be presumed when these unsaponifiable
substances have very low rotatory power and iodine number. The presence
of resin oil. may be recognised by the specific gravity being greater than
0-917 and the refractive, index above 1-51.

3.  Resin.............The soap solution remaining after the separation of the

imsapomfiuble matter is decomposed with an acid and the fatty acids then
tested by means of M'orawski's reaction (see preceding chapter:  General
Methods, 20).

For its quantitative determination Twitchell's method (ibid.) is followed.

Before applying Morawski's reaction, it is necessary thoroughly to separate
the unsaponifiable matter in order to remove the cholesterol, which gives a

similar reaction.

* *

Pure wool fat oleine should not contain more than 60% of unsaponifiable
substances. These are liquixI and have approximately the appearance of mineral
oils; they should, however, have: 0=0-900-0-917; refractive index (at
18-20°) = i-40-1-51 ; [«]„ = + 15° at least (in exceptional cases as low as
10°) and iodine number = 50-80.

(Stearic Acid)

This is a mixture of solid fatty acids (stearic and palmitic)-more or
less completely separated from, the liquid acids-obtained from animal
tallow or from some vegetable fat and used especially in the manufacture
of candles.

According to their methods of manufacture, they are distinguished as
stearins of saponific-ation and distillation stearins, the latter cpnteujun&,
unlike, the former, iso-oleic acid and2 % of unsaponi-